European Resuscitation Council Guidelines for Resuscitation ... - CPR

18 de 0ctubre de 2010 www.elsuapdetodos.com1300 C.D. Deakin et al. / Resuscitation 81 (2010) 1293–1304CardioversionIf electrical cardioversion is used to convert atrial or ventriculartachyarrhythmias, the shock must be synchronised to occurwith the R wave of the electrocardiogram rather than with the Twave: VF can be induced if a shock is delivered during the relativerefractory portion of the cardiac cycle. 183 Synchronisation can bedifficult in VT because of the wide-complex and variable forms ofventricular arrhythmia. Inspect the synchronisation marker carefullyfor consistent recognition of the R wave. If needed, chooseanother lead and/or adjust the amplitude. If synchronisation fails,give unsynchronised shocks to the unstable patient in VT to avoidprolonged delay in restoring sinus rhythm. Ventricular fibrillationor pulseless VT requires unsynchronised shocks. Conscious patientsmust be anaesthetised or sedated before attempting synchronisedcardioversion.PacingConsider pacing in patients with symptomatic bradycardiarefractory to anti-cholinergic drugs or other second line therapy(see Section 4). 113 Immediate pacing is indicated especiallywhen the block is at or below the His-Purkinje level. If transthoracicpacing is ineffective, consider transvenous pacing. Whenevera diagnosis of asystole is made, check the ECG carefully for thepresence of P waves because this will likely respond to cardiacpacing. The use of epicardial wires to pace the myocardium followingcardiac surgery is effective and discussed elsewhere. Do notattempt pacing for asystole unless P waves are present; it does notincrease short or long-term survival in- or out-of-hospital. 193–201For haemodynamically unstable, conscious patients with bradyarrhythmias,percussion pacing as a bridge to electrical pacingmay be attempted, although its effectiveness has not been established.Atrial fibrillationOptimal electrode position has been discussed previously, butanterolateral and antero-posterior are both acceptable positions.Biphasic waveforms are more effective than monophasic waveformsfor cardioversion of AF 135–138 ; and cause less severe skinburns. 184 When available, a biphasic defibrillator should be usedin preference to a monophasic defibrillator. Differences in biphasicwaveforms themselves have not been established.Monophasic waveformsA study of electrical cardioversion for atrial fibrillation indicatedthat 360 J monophasic damped sinusoidal (MDS) shocks were moreeffective than 100 or 200 J MDS shocks. 185 Although a first shockof 360 J reduces overall energy requirements for cardioversion, 185360 J may cause greater myocardial damage and skin burns thanoccurs with lower monophasic energy levels and this must be takeninto consideration. Commence synchronised cardioversion of atrialfibrillation using an initial energy level of 200 J, increasing in astepwise manner as necessary.Biphasic waveformsMore data are needed before specific recommendations canbe made for optimal biphasic energy levels. Commencing at highenergy levels has not shown to result in more successful cardioversionrates compared to lower energy levels. 135,186–191 An initialsynchronised shock of 120–150 J, escalating if necessary is a reasonablestrategy based on current data.Atrial flutter and paroxysmal supraventricular tachycardiaAtrial flutter and paroxysmal SVT generally require less energythan atrial fibrillation for cardioversion. 190 Give an initial shockof 100 J monophasic or 70–120 J biphasic. Give subsequent shocksusing stepwise increases in energy. 144Ventricular tachycardiaThe energy required for cardioversion of VT depends on themorphological characteristics and rate of the arrhythmia. 192 Ventriculartachycardia with a pulse responds well to cardioversionusing initial monophasic energies of 200 J. Use biphasic energy levelsof 120–150 J for the initial shock. Consider stepwise increases ifthe first shock fails to achieve sinus rhythm. 192Implantable cardioverter defibrillatorsImplantable cardioverter defibrillators (ICDs) are becomingincreasingly common as the devices are implanted more frequentlyas the population ages. They are implanted because a patient is consideredto be at risk from, or has had, a life-threatening shockablearrhythmia and are usually embedded under the pectoral musclebelow the left clavicle (in a similar position to pacemakers,from which they cannot be immediately distinguished). On sensinga shockable rhythm, an ICD will discharge approximately 40 Jthrough an internal pacing wire embedded in the right ventricle.On detecting VF/VT, ICD devices will discharge no more than eighttimes, but may reset if they detect a new period of VF/VT. Patientswith fractured ICD leads may suffer repeated internal defibrillationas the electrical noise is mistaken for a shockable rhythm; in thesecircumstances, the patient is likely to be conscious, with the ECGshowing a relatively normal rate. A magnet placed over the ICD willdisable the defibrillation function in these circumstances.Discharge of an ICD may cause pectoral muscle contraction inthe patient, and shocks to the rescuer have been documented. 202 Inview of the low energy levels discharged by ICDs, it is unlikely thatany harm will come to the rescuer, but the wearing of gloves andminimising contact with the patient whilst the device is dischargingis prudent. Cardioverter and pacing function should always be reevaluatedfollowing external defibrillation, both to check the deviceitself and to check pacing/defibrillation thresholds of the deviceleads.Pacemaker spikes generated by devices programmed to unipolarpacing may confuse AED software and emergency personnel,and may prevent the detection of VF. 203 The diagnostic algorithmsof modern AEDs are insensitive to such spikes.www.elsuapdetodos.comReferences1. Deakin CD, Nolan JP. European Resuscitation Council guidelines forresuscitation 2005. Section 3. Electrical therapies: automated external defibrillators,defibrillation, cardioversion and pacing. Resuscitation 2005;67(Suppl.1):S25–37.2. Proceedings of the 2005 International Consensus on CardiopulmonaryResuscitation and Emergency Cardiovascular Care Science with Treatment Recommendations.Resuscitation 2005;67:157–341.3. Larsen MP, Eisenberg MS, Cummins RO, Hallstrom AP. Predicting survivalfrom out-of-hospital cardiac arrest: a graphic model. Ann Emerg Med1993;22:1652–8.4. Valenzuela TD, Roe DJ, Cretin S, Spaite DW, Larsen MP. Estimating effectivenessof cardiac arrest interventions: a logistic regression survival model. Circulation1997;96:3308–13.5. Waalewijn RA, de Vos R, Tijssen JG, Koster RW. Survival models for out-ofhospitalcardiopulmonary resuscitation from the perspectives of the bystander,the first responder, and the paramedic. Resuscitation 2001;51:113–22.